When I read Hume, I am never disappointed. With a little guidance from Martha Nussbaum, today I found this passage in Hume:
“It may happen, in some countries, at some periods, that there be established a property in water, none in land; if the latter be in greater abundance than can be used by the inhabitants, and the former be found, with difficulty, and in very small quantities.”
When Hume was writing this, he said that water was not an issue of justice because there was plenty of it to go around, but he could see the possibility of the future we now experience. Shifting resources cause our conceptions of justice to shift (according to circumstances). Thus, justice is always dynamic and never static.